1. Field of the Invention
The present invention relates to a keyboard.
2. Description of the Related Art
There is well-known a keyboard comprising a base plate, a membrane sheet disposed on the base plate, a housing disposed on the membrane sheet, a key-top, a link mechanism disposed between the housing and the key-top, and a switching operation unit (refer to, for example, Japanese Unexamined Patent Publication (Kokai) No. 11-213806 and No. 2001-229764).
The key-top has a horizontal top portion, and a skirt portion obliquely hanging down from the horizontal top portion. A pivotal support portion of the link mechanism is disposed on an internal surface of the top portion of the key-top and an upper surface of the housing, and the link mechanism guides the key-top to drop down, keeping the horizontal state thereof, when the key-top is pushed. In the case of pushing the key-top, the key-top pushes down the switching operation unit made of a rubber and, thereby, the switching operation unit makes contact a pair of opposite connecting pieces of the membrane sheet.
In accordance with the recent requirements, a distance between the key-top and the housing is required to be short so as to realize a thin keyboard. However, when the key-top is pushed and the skirt portion of the key-top is long, a lower end of the skirt portion of the key-top (surrounding portion of the key-top) interferes with the housing. Therefore, the distance between the key-top and the housing cannot be short.